Coding and decoding method for a sequence of elements, signal, coder, decoder, corresponding computer programs and storage means

Abstract

This invention relates to a coding method for a sequence of elements that can be equal to at least two distinct values, the said elements forming at least one input symbol. According to the invention, this type of coding method comprises: a stretching step to stretch at least one of the said input symbols, to form a stretched symbol, such that the said stretched symbol does not have any successive transitions; a cancelling step to cancel the disparity of the said stretched symbol to form a coded symbol, such that the said coded symbol comprises approximately the same number of elements of each value.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] This invention relates to the field of telecommunications. More precisely, the invention proposes a new coding and decoding method for a high-speed data transmission, particularly in a home or office environment. [0003] 2. Description of Prior Art [0004] Some constraints have to be respected during the data sending and transmission phase for data transmission applications in interior and exterior environments, particularly limiting the radiation spectrum. These constraints are applicable particularly to transmissions in a home or office environment. Thus, according to electromagnetic compatibility standards in force, the radiation spectrum must respect a jig limiting radiation beyond 30 MHz. Some coding methods are used for data transmission in an intra-building environment, particularly in order to limit radiation beyond 30 MHz, while maintaining a high speed. [0005] Thus a first coding system, MLT3 (MulTiLevel 3) ...

AI Technical Summary

Benefits of technology

[0021] Another purpose of the invention is to propose a method that is easy to implement in sending and in reception, with a low cost.

[0049] According to one variant embodiment, the stretching step of the input symbol takes account of the value of a last element of the previous coded symbol so as to avoid two successive transitions.

[0052] This data scrambling step provides a means of converting the data flow into a pseudo-random flow, so as to limit the pass-band and increase the resistance to transmission parasites. In particular, this step contributes to limiting high frequencies in the signal spectrum, particularly if the same symbol is transmitted several times consecutively.

[0056] The transmission can be made on one or several cables in parallel, which can increase the useful throughput. In particular, the transmission can be made on at least one CAT-5 UTP type cable.

Problems solved by technology

Some constraints have to be respected during the data sending and transmission phase for data transmission applications in interior and exterior environments, particularly limiting the radiation spectrum.

One major disadvantage of this coding system is due to the long sequences of bits equal to “0” that appear in this code and that can cause a loss or phase shift of the receiver clock.

Coded data are scrambled before being transmitted to overcome this problem, which reduces the improvements provided by this code.

Moreover, the Hamming distance between valid code words is very small (equal to one), which facilitates transmission errors that might occur in coding or in scrambling.

There is then a risk of accepting invalid code words or rejecting valid code words.

Finally, with this code it is difficult to control the radiation spectrum and it does not have particularly interesting error detection or correction properties.

However, it has the disadvantage that it enables successive transitions.

The spectrum then does not fully respect the jig specified in frequency emission standards.

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